Option B, avoidable emergency room visits, is likely your answer.
Option A, preventative medicine, also known as prophylactic medicine is integral to better health outcomes that can help with mitigating those avoidable emergency room visits brought up in Option B. This eliminates options A and D.
Option C, expensive medications, though a pain are sometimes necessary for patients! Take insulin for example! It's mighty expensive but without it, the healthcare systems can lead to increased patient mortality! This eliminates option C.